Exacerbation still a problem even without concurrent tobacco use

Action Points

Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

People ages 40 and up who smoked marijuana, along with cigarettes or without them, appeared to increase their risk of lung exacerbation-like illnesses.

Note that the study suggests that marijuana use is not innocuous when it comes to lung disease, and that tobacco smoking, alone or together with marijuana, are risk factors for increased chronic respiratory symptoms.

WASHINGTON -- People ages 40 and up who smoked marijuana, along with cigarettes or without them, appeared to increase their risk of lung exacerbation-like illnesses, researchers reported here.

In the Canadian Obstructive Lung Disease (COLD) study of 5,106 adults over age 40, about 17% of people with an average age of about 60 who never smoked experienced respiratory exacerbation-like events in the past years compared with 19.3% of individuals who were classified as having a history of smoking cigarettes; 23.9% of people having smoked only marijuana; and 24.2% of people who smoked both marijuana and cigarettes, according to Wan Tan, MD, of the University of British Columbia in Vancouver, and colleagues.

In the Canadian Cohort of Obstructive Lung Disease (CanCOLD) study of 1.168 adults, 17.3% of never smokers experienced exacerbations compared with 26.4% of smokers, 33.3% of marijuana smokers, and 35.9% of marijuana and tobacco smokers, Tan told MedPage Today at the American Thoracic Society meeting.

In the COLD study, the difference between the dual smokers and never smokers was statistically significant (P<0.0001) and the difference was also significant between dual smokers and those who smoked marijuana only (P<0.0001), she reported.

In the CanCOLD study, the difference was significant between dual smokers and never smokers (P<0.0001) and between dual smokers and never smokers (P<0.0001). The small numbers of marijuana smokers (27) in CanCOLD made statistical analysis difficult, she noted.

"The bottom line here is: Marijuana use is not innocuous when it comes to lung disease," Tan said. "Tobacco smoking -- defined as a lifetime use of more than 365 cigarettes -- alone or together with marijuana -- defined as 50 joints or more in a lifetime -- are risk factors for increased chronic respiratory symptoms."

"Dual smoking or tobacco or marijuana synergistically increase risks for symptoms and exacerbations," she noted.

Tan pointed out that tobacco smokers were significantly more likely to experience chronic cough, chronic phlegm, wheeze, dyspnea, and sever dyspnea. Marijuana smokers were only significantly more like than non-smokers to experience wheezing, although they tended to have more chronic cough, more chronic phlegm, and more overall dyspnea.

People with both marijuana and cigarette history had more of all of the symptoms, Tan said.

Specifically, compared with people who did not smoke marijuana or tobacco, increased odds for at least one exacerbation–like event in the past 1 year occurred in smokers of marijuana only (adjusted odds ratio 1.49, 95% CI 1.56-3.30) and in dual smokers of marijuana and cigarettes (aOR 1.39, 95% 1.15-1.69).

Those who smoked cigarettes only also had an increased odds for exacerbation-like events (aOR 1.51, 95% CI 1.04-2.18), the authors reported.

ATS session moderator George O'Connor, MD, of Boston University, commented that "Dr. Tan saw a signal for sure of a synergistic effect of smoking both marijuana and cigarettes especially as it pertains to acute chest illness. I have been telling my patients this for years."

"I think we know that basically any kind of smoke ... is bad in terms of respiratory health," he told MedPage Today. "Tobacco is perhaps the worst; marijuana; even a fireplace that brings smoke into your living room. Smoke of any kind we are pretty sure is bad for you. It is just a matter of defining the risk."

"Dr. Tan's work is getting us to the point where we can have quantification of the risks," he added.

In the two studies, most of never smokers were women (38.7% were men) while the 53.3% who said they only used cigarettes were women. About 63% of those who only smoked marijuana were men and 61.4% of those who smoked both cigarettes and marijuana were men, Tan reported. Study participants ranged in age from 53-63.

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